Heretofore, the production of stainless steel has been carried out by using ferrochromium obtained through carbon reduction of chromium ore or the like in an electric furnace. However, the production of the ferrochromium was necessary to take a greater amount of electric power and the production cost thereof became high and hence the production cost of the stainless steel became also high.
As a countermeasure for solving the above problem, there has been developed so-called smelting reduction process in which chromium ore or unreduced or semi-reduced pellets of the chromium ore subjected to a preliminary treatment are subjected to carbon reduction in a metallurgical reaction vessel such as a convertor or the like without using electric power to prepare a chromium-containing molten metal (for example, JP-A-58-9959 and JP-A-55-91913).
However, the aforementioned smelting reduction process of chromium ore has still the following problems.
1) The chromium ore contains a great amount of gangue ingredient (MgO, Al.sub.2 O.sub.3 and so on), while the gangue ingredient is included in fuel and a carbonaceous material as a reducing agent, so that a greater amount of slag is created during the smelting reduction. PA0 2) In addition to the great amount of the slag, if the reduction reaction efficiency is low, the refractory is considerably lost by a metal oxide ingredient (Cr.sub.2 O.sub.3, FeO) having a high oxidizing property and also the smelting time becomes longer. PA0 3) When the carbonaceous material is charged in only a necessary amount calculated from carbon balance and heat balance, slag foaming and slopping are caused and hence the operation becomes unstable. PA0 4) Therefore, an excessive amount of the carbonaceous material is charged in the smelting reduction. PA0 1. A smelting reduction process of chromium ore by charging a carbonaceous material and a chromium ore into hot metal admitted in a metallurgical reaction vessel such as a converter or the like, feeding an oxygen gas to burn the carbonaceous material and conducting fusion and reduction of the chromium ore through heat of combustion to produce a chromium-containing molten metal, characterized in that a carbon substance having a Hardgrove grindability index (HGI) of not more than 45 and a volatile matter (VM) of not more than 10% is used as the carbonaceous material. PA0 2. A smelting reduction process according to the item 1, wherein the carbonaceous material charged in the metallurgical reaction vessel has such a particle size formation that a ratio of particle size larger than a given particle size (dp) calculated from the following equation (1) is not less than 80%: EQU dp=0.074.multidot.((Q+0.04.multidot.VM.multidot.W)/D.sup.2).sup.2/3 (mm) (1 ) PA0 3. A smelting reduction process according to the item 1 or 2, wherein the carbonaceous material is charged into the metallurgical reaction vessel in an amount that a total surface area of the carbonaceous material charged is not less than 60 m.sup.2 per 1 ton of slag existing in the vessel. PA0 4. A smelting reduction process according to the item 1, 2 or 3, wherein a portion of the carbonaceous material having a particle size smaller than the particle size calculated by the equation (1) is agglomerated. PA0 5. A smelting reduction process according to the item 1, 2, 3 or 4, wherein the reaction vessel is a converter using MgO-C bricks having a C content of 8-25% in at least a part of a portion of the vessel contacting with the slag. PA0 6. A smelting reduction process according to the item 1, 2, 3, 4 or 5, wherein a post combustion ratio inside the reaction vessel is not more than 30%.
However, when the carbonaceous material is excessively used, the amount of carbon remaining in the slag becomes large after the completion of blowing, which brings about the lowering of the utilization of the carbonaceous material and also badly exerts on the effective use of the slag.